The nitration of polycyclic aromatic hydrocarbons has been demonstrated to occur in the environment, both in the atmosphere and in combustion processes. That such nitration may have far-reaching biological consequences is demonstrated by studies carried out on the products from the nitration of pyrene. There is a complete alteration of the properties of pyrene by this substitution, a change from a nonmutagenic compound to a direct acting mutagen in the Ames test, and from a noncarcinogenic compound to a carcinogen. We propose to investigate the effects of nitration on the biological properties of another prelevant environmental polycyclic aromatic hydrocarbon, benzo(a)pyrene (B(a)P), which already has carcinogenic activity. We will study whether the introduction of a nitro group enhances or decreases this carcinogenic activity and whether there is any change in the target site for the carcinogen. The metabolism of nitrated B(a)P will be investigated and the types of metabolites formed determined. The DNA binding capability of the nitrated hydrocarbon and the various metabolites will be ascertained, and the mammalian nitroreductase which acts on nitrated benzo(a)pyrene will be identified. The importance of electronic effects in an aromatic system is demonstrated by Jerina's Bay Region Theory where calculations on the stability of carbonium ions allows prediction of carcinogenic potential. The introduction of a substituent such as a nitro group (which is strongly electron withdrawing) would alter such electronic stabilization. We therefore propose to examine the effect of position of substituent on the aromatic ring and type of substituent (electron donating or electron withdrawing) at the C-6 position of the aromatic ring, on the expression of biological activity. We hope by these studies to gain insight into the effect substituents have on carcinogenic activity.